Seoul, Oct 25 (IANS): South Korea fired warning shots at a North Korean patrol boat that crossed into its waters in the Yellow Sea, the South Korean military said on Sunday.

The South Korean navy fired five warning shots at the vessel on Saturday after it crossed the de-facto western maritime border between the two Koreas known as the Northern Limit Line (NLL) by hundreds of metres, Yonhap News Agency reported.

The boat was supposedly cracking down on dozens of illegal Chinese fishing boats in waters near South Korea's Yeonpyeong island, the military said.

The boat retreated about 18 minutes after the shots were fired, with no injuries being reported.

The North, however, condemned the firing as a "military provocation".

"South Korean belligerents carried out a military provocation against our patrol boat, which was carrying out its duties in our waters," a spokesman for the North's Committee for the Peaceful Reunification of Korea said.